The present invention relates to particulate concentrating devices, particularly such devices using centrifugal force to influence separation of heavy particulate fines from a gangue.
The rising value of rare minerals such as gold and silver has revitalized interest in prospecting, especially by individual "weekend" prospectors. The most popular method currently used by individual prospectors is hand panning. This process is extremely slow and its effectiveness varies with experience and the patience of the prospector. This, together with the low precious metal content of most "worked over" areas results in very little chance of the prospector profiting by his efforts and time.
It therefore becomes desirable to make use of apparatus that can process large volumes of material in short periods of time. Such apparatus should also be effective in separating the valued material from the gangue. It is desirable that such apparatus be fully portable and affordable to "weekend" prospectors.
Various attempts have been made to provide an efficient, if not portable, mineral concentrator throughout the years. In 1916, C. Shifferle was granted U.S. Pat. No. 1,190,466 for an apparatus that separated material of different specific gravities. The apparatus included a rotating bowl for receiving the raw material and spreading it by centrifugal force into pockets along a cylindrical upright wall. Water was urged inwardly through the wall to prevent packing of the material within the pockets. The machine had to be stopped periodically to clean the pockets. An alternate form allows continuous operation with a discharge arrangement for the collected fines. A similar concentrator is discharged in U.S. Pat. No. 2,649,202 to Jones. Neither patent discloses a bowl that is easily removable from its associated supportive framework, or an insert that is receivable within the bowl and can be removed for cleaning and replacement.
More portable apparatus is disclosed in the 1922 U.S. Pat. No. 1,413,289 to Odell et al. A hand cranked rotating drum separates material as it moves up the inclined surface of a conical base to an upright peripheral wall. The device must be partially submerged before it will operate. Also, hand cranking is not an accurate method by which consistent centrifugal forces are produced. The pan is fixed relative to the remainder of its supporting frame and therefore must be cleaned on location, as do the other apparatus already described.
A portable powered centrifugal concentrator is described by Clow et al in U.S. Pat. No. 2,858,064. Clow uses a semispherical concave bowl with an upper cylindrical rim to receive and separate material. Slots are used to receive and direct fines outwardly of coarser and lighter specific gravity tailings. Again, the bowl is substantially fixed in position on its supportive frame.
M. Schlank, in U.S. Pat. No. 2,022,926, discloses a series of riffled rotating bowls for centrifugal concentration. The bowls are fixed by bolts to their supportive rotary drives.
Another hand cranked centrifugal mining apparatus is shown in U.S. Pat. No. 942,663. This apparatus is of interest mainly because it shows the use of a renewable fabric placed within the bottom of a hand rotated dish. The fabric is intended to capture heavy minerals washed over in a slurry as the dish is rotated. Fabric naturally wears and must therefore be frequently replaced. Also, removal and replacement of the fabric and adjacent coverings is a lengthy and tedious task.
The present apparatus represents a substantial advancement in the known prior art by making use of the advantages inherent in centrifugal concentration and by eliminating the common difficulties in cleaning and readying the rotary bowl or pan for subsequent operation. It makes use of an easily removable bowl and pan insert, along with a simple and effective mechanical drive mechanism. Additional advantages are gained by the pan insert, which includes an annular flange forming a pocket in the pan for collecting fines during operation. A riffled discharge collector collects any overflow residue from the pan. The entire unit is completely portable so it may be easily transported from one site to another.